Harvard researchers have invented a so-called “bionic leaf” that produces fertilizer directly in farm soil, an innovation that could one day allow impoverished rural farmers in developing countries to make their own fertilizer on-site, significantly boosting crop yields.

The invention could be used to fight global hunger as populations expand in places like sub-Saharan Africa over the coming decades.

The researchers have already tapped their invention to grow radishes 50 percent larger than control crops raised without fertilizer, according to Dr. Daniel Nocera, who presented the findings at a press conference in San Francisco.

“I’m not saying this is an industry that’s ready to go next week,” Nocera told journalists during the annual meeting of the American Chemical Society. “I just wanted to find out if we could actually do it. And the answer is ‘Yes.’ Sometimes when you’re doing science, you just want to get to the top of the mountain to prove it can be done.”

Nocera’s current work stems from his earlier innovation unveiled six years ago: an artificial leaf that can break water down into hydrogen and oxygen using sunlight.

The new invention builds on that device. After splitting oxygen from hydrogen, it deploys a special bacteria that combines the hydrogen with carbon dioxide from the environment to create a bio-plastic. The bacteria then stores the bio-plastic as fuel internally.

“We’ve basically bottled sunlight in the form of this bio-plastic,” Nocera said.

The radishes on the right were grown with the help of a bionic leaf that produces fertilizer with bacteria, sunlight, water, and air.
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Nocera lab, Harvard University

Once the bio-plastic formed by the bacteria is placed in soil, it pulls nitrogen from the air to make ammonia, which acts as a fertilizing agent.

Advances in fertilizer played a key role in population growth during the 20th century, and commercial fertilizer now accounts for 30-50 percent of crop yields worldwide, according to various estimates.

Producing significant amounts of fertilizer typically requires large, expensive industrial facilities. In poor countries with underdeveloped infrastructure, there is a further need for distribution methods to transport the nutrient-rich substance to remote rural areas where subsistence farmers live.

“I’ve always felt the only importance of my research is, ‘Can I do the things that you already do in this society at large industrial scales with distribution systems, but in the back yard for the poor?’” Nocera said.

His breakthrough lays the technical groundwork to one day allow poor farmers in sub-Saharan Africa or rural India to produce their own fertilizer, he said.

The world population is set to boom to 9.7 billion people by 2050 from 7.3 billion in 2015, with most growth coming from developing economies, the United Nations Department of Economic and Social Affairs said in a recent report.

The highest rate of population growth is expected in Africa, which will account for more than half of the world’s population growth through 2050. By that year, the populations of 28 African countries are projected to more than double, the UN report said.